The field of the present disclosure invention is infusion pumps and relates generally to systems, apparatuses, and methods for pumping or infusing volumes of medical fluids to a patient, typically via an intravenous route.
Infusion pumps are used to infuse drugs and liquids into patients, typically via intravenous lines. While some infusion pumps deal with relatively large volumes, there may be more interest in pumps with a capability of delivering only very small controlled volumes of liquid. The drugs used may be very important, such as analgesics, anesthetics including opiates, anti-inflammatory agents, insulin, anti-spasmodic drugs, antibiotics, chemotherapy agents, cardiovascular drugs, and the like. Many of these drugs are needed in very low doses on a continuous basis, so that the patient has a steady, reliable stream over a long period of time, such as 0.1 ml per hour. If pulses are used, the dosage rate may be measure in terms of nanoliters or microliters per pulse or bolus. Regardless of whether a small volume or larger volume pump is being used, the accuracy of the pump is to a successful outcome for the patient.
Some infusion pumps have, along the length of tubing, a pumping chamber having an inlet valve and an outlet valve. The infusion fluid is admitted into a length of tubing in the pumping chamber through an open inlet valve and then isolated by occluding the tube by closing the inlet valve at an inlet of the tubing. Then, the outlet valve is opened and a pumping mechanism compresses or otherwise massages the length of tubing in question to pump or expel the fluid from the pumping chamber and towards the patient. Since the inlet is blocked by the closed valve, the liquid can only exit through the outlet, with an open valve. The outlet valve is then closed and the inlet valve and pumping mechanism opened to permit additional fluid to enter the pumping chamber from a fluid source. The above is something referred to as a singe pumping cycle or stroke.
The pumping mechanism can comprise a single pumping member that compresses the tube against a stationary block or platen. In this case the pumping member or platen may have a length substantially similar to that between the inlet and outlet valves. Alternatively, the pumping mechanism may comprise a plurality of pumping fingers or members that compress the tube in sequence. In this instance, particularly if there are sufficient pumping fingers, such that at least one is compressing the tube at all times, there may be no need for an inlet and/or outlet valves.
The accuracy of an overall infusion is dependent upon the accuracy of each pumping cycle. In other words, it is important to know with accuracy the volume of fluid pumped with each pumping cycle, to know over time the volume of the entire infusion. The volume of each pumping cycle is dependent upon the internal diameter of the tube. A problem arises due to the variability of internal diameters from tube to tube. This variability is due to, among other things, manufacturing processes and tolerances. It would be helpful for the infusion pump to be capable of determining, or measuring the internal diameter of the specific IV tube being utilized for a specific infusion. Based on this information, the pump could adjust the functionality of the pumping mechanism (speed and stroke length of the pumping mechanism) to ensure and maintain accuracy regardless of tubing inner diameter variability.
Additionally, the pump can use this information to avoid overly compressing the tube (decreases tube life due to overstressing) and under compressing the tube (leads to inaccuracies and inefficiencies).
Infusion pumps are used to accurately infuse medicines and other liquids to patients. The amount that is dispensed could be improved by an accurate knowledge of the inner dimensions of the particular tubing used to dispense a particular liquid to a patient.